1. Field of the Invention
The present invention relates to a conductive filler used for a conductive paste and conductive plastic, etc. and a method of fabricating a circuit body using the conductive paste.
2. Description of the Related Art
The conductive filler includes metallic powder, carbon powder, metallic fiber, metallic flake, metallized glass beads or metallic glass fiber. The conductive filler, which is added to an insulating or highly resistive matrix such as plastic, has been widely used to improve its electric and electromagnetic property.
The conductive fillers added to the matrix are brought into contact with each other to provide the matrix with conductivity. However, the fillers, which are in point contact with one another in most cases, give high contact resistance to hinder the improvement of conductivity.
In addition, since the conductive fillers are brought into contact with one another owing to condensing force of resin binder, the resultant matrix provides a change in the electric resistance due to changes in temperature.
In order to solve the above problem, JP-A 63-18691 proposes a technique of using filler of solder. JP-A 3-48484 proposes a technique of mixing and hardening copper paste and solder paste and carrying out heat treatment to enhance the conductivity of the surface. These techniques, however, required the heat treatment twice or could not actually give good conductivity to the matrix.